Wireless networking devices may contend for access to a shared radio-frequency (RF) spectrum by following protocol rules. The rules may be designed to increase the likelihood of access by active devices. For example, some devices, such as those operating according to protocols including an Institute of Electrical and Electronic Engineers (IEEE) 802.11 protocol, may perform a transmission back-off operation that includes delaying transmission when a busy communications medium is detected. To reduce the probability of data collisions (caused by two or more transmitters operating at the same time during an idle period following a busy period), such devices may randomly choose a particular back-off delay period (one or more time “slots”) within a maximum delay period, referred to as the “contention window.”
The contention window may grow exponentially according to the protocol as the wireless networking device senses recurring instances of a busy medium condition and/or performs a back-off in response to each instance. The device may sense the busy medium condition by detecting RF energy in a received spectrum, perhaps originating from other wireless networking devices transmitting on the same channel(s), utilizing the same modulation technique, and/or obeying the same protocol (hereinafter referred to as “coherent energy”). On the other hand, in-band received energy may originate from an interference source (e.g., a microwave oven) not participating in the protocol. Such interference source operation may cause the contention window associated with the device to reach a maximum value, preventing and/or reducing transmissions from the device. System throughput may decrease as a result.
For more information regarding IEEE 802.11 standards, please refer to “IEEE Standards for Information Technology—Telecommunications and Information Exchange between Systems—Local and Metropolitan Area Network—Specific Requirements—Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY), ISO/IEC 8802-11: 1999” and related amendments.